The present invention relates to the recovery of hydrocarbons from petroleum reservoirs, and it relates particularly to the use of chemical microexplosions to recover hydrocarbons from these reservoirs.
During primary depletion, wells flow by natural drive mechanisms such as solution gas, gas cap expansion and water flux. In the secondary recovery phase water or gas injection is usually used to maintain reservoir pressure and to sweep out more hydrocarbons. However, a significant amount of hydrocarbons remain unrecovered due to capillary forces and reservoir inhomogeneities. This hydrocarbon fraction is not swept by gas and/or water flooding.
It is known to use physical vibrations produced by surface or downhole sources to mobilize trapped oil. This technology is based on claims and observations, that earthquakes, mechanical and acoustic vibrations increase oil production. Practical and effective demonstration of the technology is yet to be established.
It is also known to use heat to cause viscous oil to flow. U.S. Pat. No. 4,867,238, Bayless, disclosed injecting hydrogen peroxide into a hydrocarbon reservoir and using the heat from its decomposition and combustion of hydrocarbon to cause viscous oil to flow in the reservoir. U.S. Pat. No. 3,075,463 by Eilers; 3,314,477 by Boevers; and 3,336,982 by Woodward disclosed injecting two or more chemicals that react in situ to generate heat to stimulate oil recovery. The chemicals used in the prior art processes tended to react rapidly to produce large explosions and shock waves that fractured formation rock. In many of the prior art processes, the fracturing was the ultimate goal. An improved, less violent process is needed for generating heat, pressure, and vibration in situ to stimulate hydrocarbon production from the formation.
The present invention discloses an improved method of generating in a hydrocarbon-bearing formation heat, pressure, and a rapid physical vibration (a microexplosion that generates a microshock). Microexplosions are defined as the process by which chemicals rapidly react to generate microexplosions and micro-pressure waves in addition to heat and pressure to coalesce and drive hydrocarbons out of a hydrocarbon-bearing formation such as an oil reservoir. A preferred process of this invention reacts in situ an imidazolidone with an acid to produce heat, vibration, and CO2.
There are several advantages to this invention: (1) the microexplosion can be controlled to trigger in a specific time and place, and (2) the magnitude of the explosion can be controlled by concentration variation and molecular design. The method stimulates hydrocarbon recovery by generating physical microshock and vibration, by generating pressure and heat which improve hydrocarbon mobility and gaseous by-products of the in situ reactions improve hydrocarbon mobility.